Power actuated thermostatic switch

ABSTRACT

A thermostat that has a quick opening and closing of the electrical switching contacts due to an electromagnetically actuated mechanical force acting directly on the contacts. The thermally responsive bimetal electrical contact connection initiates a relay-like function which causes the electrical contacts of the thermostat to positively close and open in a few thousandths of a second. This results in extended contact life and extended precise calibration retention. By the use of a solenoid and its mechanical force the thermostat provides for a clean quick break open and a quick firm positive pressure closing of the electrical switching contacts.

United States Patent [191 Lightgarn Oct. 8, 1974 POWER ACTUATED THERMOSTATIC SWITCH [76] Inventor: Fred Lightgarn, 314 Evonshire St.,

Santa Barbara, Calif. 93111 [22] Filed: June 9, 1972 [21] Appl. No.: 261,165

[52] US. Cl. 337/366, 335/145 [51] Int. Cl. H01h 37/66 [58] Field of Search 337/366, 90; 335/145 [56] References Cited UNITED STATES PATENTS 1,981,934 9/1932 Werner 2,740,923 4/1956 Loeber...-. 3,501,718 3/1970 Chambers Primary Examiner-Harold Broome 5 7 ABSTRACT A thermostat that has a quick opening and closing of I the electrical switching contacts due to an electromagnetically actuated mechanical force acting directly on the contacts. The thermally responsive bimetal electrical contact connection initiates a relay-like function which causes the electrical contacts of the thermostat to positively close andopen in a few thousandths of a second. This results in extended contact life and extended precise calibration retention. By the use of a solenoid and its mechanical force the thermostat provides for a clean quick break open and a quick firm positive pressure closing of the electrical switching contacts.

1 Claim, 1 Drawing Figure POWER ACTUATED TI-IERMOSTATIC SWITCH BACKGROUND SUMMARY Due to the positive and forcible mechanical opening and closing of the electrical switching contacts in the cally insulated from the blade arms. Blade arm is the thermally responsive bimetal on which is mounted contact 15a. Blade arm 17 is made of a relatively stiff metal with only a slight amount of resiliency and on it is mounted contacts 17a and 17b. Blade arm 19 is made of a springy metal and has normally open contact 19a mounted on it. The bimetal blade arm 15 is adjusted by set-screw 22 which has a ceramic end piece 23 attached to it and which passes through holes, not shown, in the blade arms 17 and 19. An electro-magnetic mechanical push action solenoid is 24 with actuating plunger 25 having a ceramic tip 25a attached to it. A

bimetal temperature sensing circuit of this invention the contacts are protected against excessive arcing and sparking so that they will retain a close temperature differential calibration within a few degrees for over 500,000 cycles. In contrast, many commercially avail able thermostats can only maintain their calibtation for a relatively short number of cycles: from 5000 to 25,000.

Also due to the positive and forcible mechanical opening and closing of the electrical contacts in the load switching circuit, this invention provides for extended contact life while carrying very heavy loads. Many commercially available thermostats are completely worn out under heavy load conditions in 200,000 cycles or less due to arcing and sparking. In contrast, this invention provides for a load contact life of over 500,000 cycles and up to 5 million cycles.

In this invention the electrical contacts are forcibly closed under mechanical pressure once the first momentary electrical connection is made by the bimetal blade contact in closing an electrical circuit to an electro-magnet such as a solenoid. Upon the opening of the bimetal circuit the solenoid releases its mechanical pressure and the electrical contacts immediately open wide apart due to spring actionin one of the nonbimetal blade arms. Thus the closing time and the opening time of the electrical contacts is measured in thousandths of a second instead of tenths of a second. In the preferred embodiment of the invention the bimetal contacts only switches the very low solenoid current which can be as low as 5 watts. Thus the bimetal electrical contact life is greatly extended. The load switching contacts are able to handle much larger than normal loads for extended cycles because they open and close-so quickly. A feature of the invention is that direct mechanical action by a solenoid operates simultaneously on both the bimetal control switching contacts and the load switching contacts.

The specific nature of the invention, as well as other objects and advantages thereof will appear from the following description and drawings.

FIG. 1 shows a side view of the preferred embodiment.

As shown in FIG. 1, the thermostat assembly is supported by rigid member 21. Insulators 14,16,18 and 20 hold blade arms 15,17, and 19 in position. Bolts 11 and 12 are threaded into metal end piece 13 and are electrifull wave rectifier 26 supplies direct current to solenoid 24. The electrical load is represented by 27 to facilitate understanding of the invention.

In operation, upon a change of temperature bimetal arm 15 and contact 15a moves over to make electrical connection with contact 17a. Within a few thousandths of a second solenoid 24 is energized and forces push ac- .tuator 25 and 25a to-exert a positive mechanical pressure on contact 19a which then moves over and makes firm electrical connection with contact 17b to close the load circuit to load 27. 'Due to the direct mechanical force exerted by the solenoid 24 not only is the load switching circuitpositively closed but, in addition, the bimetal control switching circuit to the solenoid 24 is also positively closed because when contact 19a is pressing against contact 17b there is enough extra pressure available to slightly move contact 17a a few thousandths of an inch' towards contact 15a to provide the positive closure necessary to avoid all hesitancy, uncertainty or chatter which in turn reduces arc and spark deterioration of the contacts to a minimum. As a direct result of this additional mechanical movement plus the low current load of 5 watts for the solenoid, contacts 15a and l7ahave an extended life and will substantially retain their set point temperature calibration for 500,000 cycles or more.

Upon another temperature change bimetal blade arm 15 and contact 15a move away from contact 17a to open the solenoid circuit. With solenoid 24 deenergized, within a few thousandths of a second, spring arm 19 springs back opening the load circuit and also releasing mechanical pressure on contact 17a so that stiff blade arm 17 and contact 17a move apart still further from contact 15a and thus providing more physical separation of the contacts than what was possible by the action of the bimetal movement alone. v An important factor in this invention is that the thermostatic bimetal blade arm 15 and its electrical contact 15a has unrestricted and unencumbered freedomof movement so that it will respond to relatively small temperature changes. This is because there is no magnetic attraction or any othermagnetic or mechanical influences acting as a restraint that must be overcome first before the thermostat can respond to a change in temperature.

Another factor in this invention is that the thermostatic blade arm 15 is physically assisted to a slight but significant amount in its movement in one direction when it is responding to a temperature change in that direction. The explanation is as follows: as the blade arm contact 15a moves over and touches contact 17a it results in the solenoid 24 being energized. Thus plunger 25 immediately operates to exert a mechanical pushing force on contact 19a to move it over and forcibly push upon contact 17b and 17a and move them over slightly also. Since contact a was already touching contact 17a it then too, along with blade arm 15, is forced to move slightly backwards-122 in reverse of the motion that was taking place which resulted in the making of the electrical connection which energized the solenoid 24. Thus when a reverse motion of blade arm 15 is in order, at a later time interval, in response to another change of temperature, its motion in that direction is facilitated by the slight mechanical bias which is steadily applied to it as long as the solenoid 24 is energized. It is to be understood that since blade arm 17 is relatively stiff and only slightly resilient it limits the backwards movement of blade arm 15 to only a few thousandths of an inch but which is sufficient to insure a good solid electrical connection between contact 15a and contact 17a.

It is apparent that various changes and modifications and arrangements could be made in the above constructions witout departing from the scope of the invention as all matter contained in the above description or what is shown in the drawings shall be interpreted as being illustrative only and not in a limiting sense.

What is claimed is:

1. In a thermostat having two electrical circuits, comprizing in combination, a support on which are mounted;

a. a first bimetal thermally responsive blade arm having an electrical contact on one movable end and free of any magnetic attraction acting upon it;

b. a second blade arm having one movable end with two electrical contacts and free of any magnetic attraction acting upon it, with one of the said electrical contacts co-operative with the said electrical contact on the first said blade arm to control a primary electrical circuit including an electromechanical force means and which is made of a slightly resilient relatively stiff metal which returns to a normal position after being moved by an external mechanical force;

c. a third blade arm having one movable end with an electrical contact and with the said electrical contact cooperative with the second electrical contact of said, second blade arm and acting to control a secondary electrical load circuit, and which is made of a springy flexible metal which returns to a normal position after being moved by an external mechanical force;

d. said electromechanical force means adapted to mechanically force the mechanical closing of the said secondary load circuit co-operative electrical contacts and to simultaneously act to increase the mechanical touching pressure of the said first bimetal thermally responsive blade arm electrical contact against the co-operative electrical contact on the said second blade arm when the said electromechanical force means electrical circuit is energized through the initial closing of the said primary circuit electrical contacts;

c. with means to adjust the calibration of the said first thermally responsive blade arm with its electrical contact.

Patent No. Dated Inventqq 7 red Lichtg It is certified thaterrqr appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Item [76] should read Lichtgern" Signed and sealed this 7th day of. January 1975.

(SEAL) I Attest: McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (IO-69) u'coMwDc UM, I IIJ. GOVII IIUIT PIINIIIG OIIICI I". 0liO-SSI.

" UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. Q' I balked 10-18-74 Inventor) Fred Lichtgarn It is certified thaterror appearsin the above-identified patent and that said Letters Patentare hereby corrected as shown below:

Item [76] should read Lichtger'n" Signed and sealed this 7th day of. January 1975.

(SEAL) A Atte-St:

McCOY M. GIBSON JR. Attesting Officer- C. MARSHALL DANN Commissioner of Patents FORM PC4050 (0-69) us. covqnuu r mamas omc: nu o-au-nn. 

1. In a thermostat having two electrical circuits, comprizing in combination, a support on which are mounted; a. a first bimetal thermally responsive blade arm having an electrical contact on one movable end and free of any magnetic attraction acting upon it; b. a second blade arm having one movable end with two electrical contacts and free of any magnetic attraction acting upon it, with one of the said electrical contacts co-operative with the said electrical contact on the first said blade arm to control a primary electrical circuit including an electromechanical force means and which is made of a slightly resilient relatively stiff metal which returns to a normal position after being moved by an external mechanical force; c. a third blade arm having one movable end with an electrical contact and with the said electrical contact co-operative with the second electrical contact of said second blade arm and acting to control a secondary electrical load circuit, and which is made of a springy flexible metal which returns to a normal position after being moved by an external mechanical force; d. said electromechanical force means adapted to mechanically force the mechanical closing of the said secondary load circuit co-operative electrical contacts and to simultaneously act to increase the mechanical touching pressure of the said first bimetal thermally responsive blade arm electrical contact against the co-operative electrical contact on the said second blade arm when the said electromechanical force means electrical circuit is energized through the initial closing of the said primary circuit electrical contacts; e. with means to adjust the calibration of the said first thermally responsive blade arm with its electrical contact. 